1. Field of the Invention
This invention relates to the combined desulfurization and hydroconversion, and consequent upgrading, of sulfur-bearing hydrocarbon feedstocks by contacting the feedstock with an alkaline earth metal hydride or oxide in the presence of hydrogen and at elevated temperatures.
2. Description of the Prior Art
The problem of air pollution, particularly with regard to sulfur oxide emissions, has been of increasing concern to refiners. As a consequence, the development of efficient as well as economic means for the removal of sulfur from sulfur-bearing fuel oils has become a primary research goal in this industry. Presently, the most practical desulfurization process is the catalytic hydrogenation of sulfur-containing molecules in petroleum hydrocarbon feeds to effect the removal of these sulfur molecules as hydrogen sulfide. The process generally requires relatively high hydrogen pressures, e.g., from about 700 to 3000 psig and temperatures in the range of about 650.degree. F to 800.degree. F depending on the feedstock and the degree of desulfurization. Also, these processes do not effect the simultaneous desulfurization and hydroconversion of the feedstocks employed, and particularly not without a high degree of coke make during same.
The catalytic process is thus generally quite efficient in the handling of distillates, but becomes more complex and expensive and less efficient as the feedstock becomes increasingly heavier, e.g., whole or topped crudes and residua. Thus, for example, a residuum feedstock is often times contaminated with heavy metals, e.g., nickel, vanadium, iron, and asphaltenes which tend to deposit on and deactivate the catalyst. Also, the sulfur is generally contained in high molecular weight molecules that can be broken down only with the aid of severe operating conditions. Such operating conditions, however, tend to accelerate catalyst deactivation due to the accelerated depositions of coke and metal on the catalyst surfaces.
It has also long been known that alkali and alkaline earth metals, as well as their corresponding hydrides, hydroxides and oxides, exhibit desulfurization activity for residua, but even so suffer from distinct drawbacks, such as poor desulfurization efficiency, a tendency to produce oil insoluble sludges, the inability to upgrade the feedstock by demetallization, and the formation of salt-oil mixtures that are exceedingly difficult to resolve by conventional means. Furthermore, again, none of these materials has ever been employed to obtain the simultaneous desulfurization and substantial hydroconversion of the feedstocks being treated.
As an example of such a prior art process, U.S. Pat. No. 1,865,235 to Cross discloses the use of sodium, calcium, potassium, magnesium, strontium, barium and lithium in their metallic form or as hydrides thereof by contacting such materials with oils to be desulfurized at relatively low temperatures. Furthermore, U.S. Pat. No. 2,002,747 to Morrell discloses a method for the desulfurization of hydrocarbon oils wherein metals of the alkali or alkaline earth groups, preferably in a molten state, together with gases such as ammonia, steam and air react with cracked hydrocarbon vapors to produce sulfides of the metals involved, hydrogen sulfide and hydrogen in a state sufficiently reactive to substantially saturate the olefinic constituents of the vapors. The above reaction is generally carried out at a temperature of the order of 750.degree. to 1000.degree. F, under a pressure of the order of 100 to 500 psig. U.S. Pat. No. 3,633,433 to Fraini relates to a process for reducing the sulfur content of hydrocarbon oils by reacting such feedstocks in a hydrogen atmosphere with finely divided magnesium, at a temperature in the range of 600.degree. to 850.degree. F under a pressure of 100 to 200 psig and employing a hydrogen flow rate of 0.5 to 1.5 moles hydrogen per mole of feedstock per hour. Once again, however, none of these processes employ the materials of the present invention in order to obtain simultaneous desulfurization and hydroconversion.
While these techniques have thus proven successful with regard to desulfurization, the search has continued for improved desulfurization processes which are capable of effecting significant simultaneous hydroconversion, and for improved methods for regenerating the products produced by the contact of the desulfurization agent in the reaction zone.
It has now been found that when alkaline earth metal hydrides, oxides and mixtures thereof, especially barium hydride and barium oxide, are contacted to react with sulfur-bearing, heavy petroleum oil feedstocks, in the presence of hydrogen, at elevated temperatures, the feedstock undergoes desulfurization and demetallization while, simultaneously, heavy constituents of the feedstock undergo hydroconversion to lighter, lower boiling components. Thus, in effect the use of alkaline earth metal hydrides or oxides in conjunction with the hydrogen as described herein results in a combined and simultaneous desulfurization and hydroconversion of the feedstock which may be effected in an efficient and economical manner. In the past it has not been known to subject such feedstocks to such hydroconversion in the presence of such materials.